Bicycle has been used as a transportation vehicle since it was created. In recent years in advanced countries, in order to save energy, many people would take a bicycle for short range traveling instead of a motorized transportation vehicle. And at the present time, bicycle is also mainly used as an outdoor sports activity.
Although bicycle is widely used in all countries by all people, there is still few criterion regarding safety riding of a bicycle. Following the fast development in technology, bicycle is designed to become more compact and light. However, there is little change on stop warning system. Although there are various kinds of bicycle tail lamps been commercialized, or various kinds of light reflector pads been used to stick to the tail portion of a bicycle, these bicycle tail lamps or light reflector pads just give a signal to indicate where the bicycle is, and they are not applicable to simultaneously show a braking situation. Further, few countries had ever paid attention to guiding the people in riding a bicycle. More particularly to those young people or children, they may have little common sense pertaining traffic regulations. Because a bicycle has nothing to protect the rider, it is indeed dangerous to ride a bicycle in the night. Since a bicycle is very light and its speed is slow, while riding on a road, it may be attacked by a fast passing motorcycle or motorcar from the back to cause accident. Therefore, it is one of the best methods to protect a bicycle rider to have a bicycle equipped a means to give a warning signal to the motorcycle or car drivers coming behind when to stop.